It's not a bad idea to think about water. Though Earth is literally overrun with water only 2% is usable and current energy and technology limitations make it impractical to bring it to the areas that need it most, so management is important.

Water is the limiting factor for many plants and trees and climate models project hotter and drier summers for much of the globe. An international research team is studying which factors govern the resistance of tropical trees to periods of drought and fins that stored carbohydrates play a key role in the resilience of the individual plant.

While stored starch and soluble sugar in plant tissues were thought to influence the resistance and resilience of trees positively during periods of drought, this supposition had not been proven. Michael O'Brien, an ecologist at the University of Zurich, and colleagues planted 1,400 saplings of ten different tropical tree species in Malaysia and devised a novel experiment to manipulate the carbohydrates stored and observe their reaction.

Malula Field Station in Malaysia. The experiments are conducted under controlled conditions in the large, black cubes. The installations are large enough to be able to grow the tree saplings unrestrictedly.Credit: Michael O'Brien/UZH

The researchers increased or decreased the concentration of stored carbohydrates and exposed the seedlings to an artificial drought period. It became clear that young trees with more stored carbohydrates were able to maintain the vital water content in the stem for longer than those with fewer stored carbohydrates.

"The better drought resistance and thus the greater chance of surviving a period of drought evidently depends on the quantity of carbohydrates stored," concludes O'Brien.

Carbohydrate content different in every tree species

According to the scientists, the ability to store carbohydrates varies both within and between species: "As different trees display a different mortality due to aridity, the impact of a forest decline triggered by climate change is cushioned," O'Brien is convinced. These new insights are also significant for reforestation: The planting of species that store more carbohydrates can be favored to boost the forests' resistance to the drier climates predicted by the climate change models.

The Danum River in Sabah, Malaysia, Borneo. The colorful trees are currently in bloom. The blossoming of tropical trees is often triggered by periods of drought (dry spells, blossoming and recovery are closely intertwined in tropical systems).Credit: Michael O'Brien/UZH